How MLB and T-Mobile’s ABS Challenge System Fixes Strike Calls in Seconds

Baseball can be a game of physics and statistics, so I was surprised at a recent major league game in Seattle when a technical move sent the crowd into a frenzy.

In the May 1 game, Kansas City Royals pitcher Cole Ragans threw a fastball to hit Leo Rivas of the Seattle Mariners toward the lower left corner of the strike zone. The referee called a strike, putting Rivas out – until Rivas tapped his helmet twice.

This gesture activated an automatic ball strike challenge, or ABS, to review the pitch, which must be triggered within seconds of catching the ball.

All eyes turned to the big screen to watch an animation of the field. This showed, empirically, that the ball had indeed nicked the corner of the strike zone, confirming that the referee had made the right call, much to the disappointment of the crowd.

ABS is the product of a collaboration between Major League Baseball and T-Mobile. The technology was called up to the major leagues this season after more than 7,000 minor league test games. The system is now used in all 29 MLB stadiums in the United States (the Toronto Blue Jays ballpark has not deployed ABS because T-Mobile is not licensed to operate in Canada).

Speaking at T-Mobile Park in Seattle before that early May game, John Stanton, owner and president of the Seattle Mariners (and founder of VoiceStream Wireless, now T-Mobile), explained that the challenge system was developed after new television technology changed the way people experienced the game.

Unlike fans in the stadium who rely on calls from the umpire behind home plate, viewers at home could clearly see whether pitches were balls or strikes, thanks to a visible box for the strike zone on television.

“It became evident when there was a bad call. And the umpires were embarrassed by it, and we were in a situation where it undermined some of the credibility of baseball,” Stanton said. “It was important to find a way to solve this problem.”

How the ABS system calls strikes and balls

Behind the scenes – or rather around the park – are 12 Hawk-Eye cameras pointed at the mound and home plate to track pitchers’ handoffs and ball movement.

They communicate over a private T-Mobile 5G network within the park using Ericsson Dot radios, easily overlooked finned discs the size of dinner plates mounted in various locations, including each team’s dugout and the press box above home plate. The network uses N41 (2.5 GHz) spectrum licensed from T-Mobile to minimize interference.

Low latency, which averages about 2.3 milliseconds, is also critical to the network, according to a LinkedIn post by T-Mobile’s John Saw, president of technology and chief technology officer.

The ABS system analyzes the field, creates an animation of where the ball landed in the strike zone and projects it on the big screen for fans in the stadium to see. T-Mobile’s internal goal is a 17-second turnaround time from the moment the player taps their head. Stanton said that, in practice, this happens on average in 15.4 seconds.

While it could be argued that the animation of the pitch crossing the plate and appearing in a magnified representation of the strike zone is not technically necessary, it is surely more compelling to the audience than a simple binary decision as to whether or not it is a strike. Preparing for the call can seem as dramatic to the crowd as waiting to see if an outfielder will catch a high ball.

“When a decision is made, the fans, the refs and the players all find out at the exact same time,” Stanton said, creating “that hold-your-breath dynamic that is particularly special.”

MLB maintains a video recording of all ABS challenges in the MLB Film Room, but fans can visit the official ABS website to dig deeper into how technology is affecting teams and players this year. At the forefront are statistics showing that currently, 53% of calls have been overturned by an ABS challenge at this point in the season.

While this ostensibly suggests that umpires are missing calls, players are only asking for reviews of the most uncertain situations – and anyone who has seen an ABS result knows how those pitches often barely touch the edge of the strike zone.

Does instant data ruin the spirit of the game?

What about baseball purists who see this as an encroachment of technology on a game that relies on the eyes and judgment of skilled players and umpires? I expected that fans who think ABS dulls the core of the game would be even more opposed to even greater adoption of data over tradition, a la Moneyball.

T-Mobile’s Amy Azzi, vice president of sponsorships for sports, entertainment and hospitality, said sentiment was their biggest point of nervousness. But MLB shared statistics with T-Mobile showing that 91% of respondents said ABS improved the game overall, and 76% said it improved the gaming experience.

“This stadium lights up when a call is overturned, or it becomes a rallying moment for the crowd,” Azzi said.

Each team receives two ABS challenges during a game. If a challenge is canceled, the team that completed it loses one of its challenges. If it is accepted, the team keeps the challenge and can reuse it later. So, if a team challenges two calls that it thinks are strikes and the ABS system confirms that they are strikes, the team can still make further challenges until it loses them.

ABS also adds another strategic element to the game. Jerry Dipito, president of baseball operations for the Mariners, said the team is learning that patience counts.

“We always appreciate the patience and thoughtfulness of our players,” said Dipito, noting that it is even more important today with this technological option. “All we need to do is press the switch at the right time during an ABS challenge to affect the outcome of a match.”

Even with precision ABS technology, it still doesn’t remove the human factor. Dipito gave the example of a game against the Minnesota Twins, who he said were aggressive in using ABS challenges. They had run out of challenges in the sixth inning, and when they got to the ninth, Seattle threw two pitches that would have been identified as balls if a challenge was available.

However, Mariners catcher Cal Raleigh presented the pitch as a strike, something he’s always been very good at, Dipito noted.

“[Raleigh] actually turned the game in our favor because he made it look like a strike,” he said.

Although the Mariners ultimately lost the early May game 7-6, it was still exciting to watch in person, with five homers, four ABS calls and a home team comeback that almost prevailed. At the end of the day, despite all the data and statistics, it’s still the experience that counts.